Joe Lhota once worked on Wall Street, but he’s clearly no vampire squid.

Long before he became one of then-Mayor Rudy Giuliani’s top aides, Lhota was an investment banker whose specialty was helping cities and states raise cash to build roads and bridges. He was highly sought-after — but different from many colleagues.

Lots of guys would sell their souls in a heartbeat to work at Goldman Sachs, the infamous “vampire squid” firm, known both for showering huge bonuses on its bankers and screwing its clients to make a quick buck. But when Lhota did succumb to an offer from Goldman, he only spent a couple of days there — and walked out after getting a first-hand whiff of its back-stabbing corporate culture.

“They didn’t even have time to put me into the computer system,” he told me recently.

That was just one of Lhota’s stops over the past two-plus decades, which include beating cancer (Hodgkins lymphoma) as well as high-powered jobs in the private sector and government.

He recently won high praise as MTA chief for getting mass transit up and running after Sandy — aides to Gov. Cuomo called him a “superstar,” while Cuomo himself said he’d done an “extraordinary job.” But people forget his experience as a deputy mayor under Rudy — including getting the whole city up and running after 9/11.

All that gives Lhota the most impressive resume in the race to succeed Mayor Bloomberg — if he runs. (He can’t officially do anything until he leaves the MTA at year’s end.)

Of course, it takes more than degrees from Harvard (Lhota has an MBA) and top jobs in government and business to be a successful mayor, where every word is scrutinized and plain talk is liable to get you in trouble.

And Lhota is definitely a guy who speaks his mind.

One outburst came when he vociferously defended Rudy’s call to remove an obscene (and utterly disgusting) painting of the Virgin Mary from a city museum because “it would be inappropriate for my daughter to see.” More recently, he called Bloomberg an “idiot” over the mayor’s comments on reopening the Midtown Tunnel after Sandy.

He’s had to apologize quite a few times, blaming his indiscretions on his “Bronx upbringing.”

But coming from The Bronx has made Lhota a fighter, and it’s something he’d surely bring to City Hall. The son of a New York City cop, he’s quick to draw a distinction between himself and Bloomberg, a Boston native who famously lives in his Manhattan townhouse.

“I grew up in The Bronx and I live in Brooklyn and I’m not going to be a Manhattan-centric mayor,” he says. “I know what the boroughs need: jobs, better transportation and, maybe most of all, attention. Too much now seems to be centered on New York County.”

While still heading the MTA, he can’t provide too many details about exactly how he’d run the city differently — but he gave some clues in our interview.

Among the many jobs he held under Giuliani was city budget director, so he’s immersed in the nitty-gritty of the city’s revenues and expenses. He understands that the city faces a tremendous task in paying for a government that continued to grow under Bloomberg, while revenues from Wall Street will continue to shrink.“The goal of any mayor,” he says, should be making sure the public sector doesn’t crowd out private-sector growth.

That means being tough with the municipal unions. “The first priority, no matter who is mayor, will be dealing with the unions, because all collective-bargaining agreements are ending and they’re just waiting for the next mayor to make their move.” They’ll want concessions the city can’t afford; higher taxes would make New York even less welcoming to businesses than it already is.

Lhota says the Democratic mayoral wannabes like Speaker Christine Quinn are playing a dangerous game of sucking up to the union chiefs when they should be mindful that the city has to find a way to keep the size of government manageable.

“We have to create jobs,” he says. “Without jobs, there are no revenues and without revenues we don’t have the money to pay for all this stuff. It’s pretty simple.”

How does he rate his chances? The Joe Lhota I know (for more than 20 years) is a realist who knows that, if he runs, it’ll be an uphill battle.He reminds me that he’d first have to get through a GOP primary where he’d likely face billionaire grocery-store magnate John Catsimatidis and possibly former NYSE chief Richard Grasso, among others.

And then he’d face a local media hostile to both Republicans and businessmen who run for public office, not to mention the city’s entrenched Democratic establishment.